In recent years, in the field of NAND type flash memory, NAND type flash memory devices of laminating type (three-dimensional type) are attracting attention, as devices enabled to achieve high integration without resolution limit of lithography technologies.
Such NAND type flash memory devices of three-dimensional type comprise a stacked body configured by alternately stacking conductive films which function as word lines or select gate lines and interlayer insulating films. In addition, It also comprises semiconductor layers formed to penetrate the stacked body. These semiconductor layers function as bodies of the memory strings. A memory film including a charge storage film is formed between the semiconductor layer and the conductive films.
In such NAND type flash memory devices of three-dimensional type, ON/OFF properties of the select transistors (selection characteristics) are important. It is necessary to flow a sufficient current when it is selected, while it is necessary to suppress a leak current when it is not selected. On the other hand, in the NAND flash memory of a three-dimensional type, an area of a wiring region for connection to various wiring lines is required to be reduced.